bychinsky



Jan. 31, 1956 w. A. BYCHINSKY IGNITER PLUGS 2 Sheets-Sheet 1 Filed May21, 1952 3nvenf0r W 9 m (Ittornegs 2 Sheets-Sheet 2 3 11 men for Kai/hm@Zfiyclzhsy (Ittornegs Jan. 31, 1956 w. A. BYCHINSKY IGNITER PLUGS FiledMay 21, 1952 m a 8 a m a M W M 8 5 i i 3 8 M w I m mqw 4 6 III 252IGNITER PLUGS Wilfred A. Bychinsky, Ann Arbor, Mich., assignor toGeneral Motors Corporation, Detroit, Mich., a corporation of DelawareApplication May 21, 1952, Serial No. 289,158 6 Claims. (Cl. 317-83) Thisinvention relates to spark plugs and, more particularly, to spark plugsespecially suitable for use with high voltages as igniters in jet engineburners.

it often occurs that the fuel mixture which is fed into jet engineburners is quite poor and ditficult to ignite, perhaps because themixture is too lean or too rich or because the fuel is not completelyvaporized. This is particularly true when operation is at high altitudeunder which conditions it is often quite diflicult to ignite and tomaintain ignited the fuel mixture which is blown into the burner at highspeed. it is well known that an igniter having a spark gap which isconsiderably larger than the ordinary is effective to cause a morecomplete ignition of the fuel mixtures and is therefore beneficial forincreasing the eificiency of the burner. An increase in the size of thespark gap demands the use of a much higher voltage than that usuallyused and thus increases the problem of electrical insulation in theigniter. If a conventional ground return type plug is redesigned bywidening the spark gap and providing the extra amount of insulationrequired by the application or" higher voltages, various difiicultieswhich are inherent in such a design preclude efficient and satisfactoryoperation. The problem of adequately cooling the igniter becomes moreditficult when increased amounts of electrical insulation are used.Also, larger and more complex insulators must be manufactured. Such asystem likewise increases the problems of electrically insulating theentire ignition wiring system since the entire voltage load is carriedby a single circuit.

It is an object of this invention to provide an igniter having a largerthan ordinary spark gap to operate at high voltage, but which avoids theproblem of high tension insulation. Another object of the invention isthe provisic-n of an igniter plug which is designed to operate at highvoltages and which has adequate cooling means, both for the electricalinsulator and supporting members and for the electrodes.

These and other objects are carried out by the provision of an igniterhaving a spark gap formed between a pair of air conducting hollowelectrodes, each of the electrodes being insulated from ground by a pairof vertically arranged insulators the structure of which cooperates withthe insulator supporting shell to provide for the passage of cooling airthrough the electrode and insulators, the igniter operating inconjunction with a two-coil ignition system.

Other objects and advantages will appear more clearly from the followingdescription of specific embodiments of the invention and from theaccompanying drawings in which Figure l is a side view of one embodimentof the invention with one half of the igniter shown in section; Figure1A is an enlarged cross-sectional view of the upper portion of theelectrode shown in Figure 1; Figure 2 is bottom view of the embodimentshown in Figure 1; Figure 3 is a view taken on the line 33 of Figure 1;Figure 4 is a view taken on the line 44 of Figure 1; Figure 5 is a sideview with parts broken away of another embodiment tinite rates Patentnice 2,733,385 Patented Jan. 31, 1956 of the invention, and Figure 6 isa bottom view of the modification shown in Figure 5 Referring now to thedrawings, Figure 1 shows an igniter consisting of two units 3 and 10mounted side by side in parallel spaced relationship on a mounting plateor pad 12. With the exception that the electrodes are bent in oppositedirections as hereinafter discussed, these units are identical and thusthe description and reference numerals hereinafter used are applicableto either of the units except as specified otherwise.

Each of the units includes a metal outer shell 14, a pair of verticallyarranged insulators 16 and 18, and an electrode 2%. Mounted on the topof and concentrically with the shell is a metal shield 22 externallythreaded at 24 for The shield 22 is secured to the shell by soldering orbrazing and by means of the metal ring 26 which is brazed or solderedboth to the shell in and to the shield 22. The shield and shell may ofcourse be integral so long as means is provided for assembly of theinsulators and electrode therein.

The lower insulator 16, which has a center bore 28 with an upper end ofenlarged diameter, a lower sleeve portion which extends below the shell14, and an external annular shoulder 34-, is supported in the shell 14by a support ring so which in turn is held in the shell by means of theindentation 38 provided thereon.

In the particular embodiment shown, the shell 14 consists of sheet metaland thus the support ring 36 and indentation 33 provide a convenientmeans for supporting the insulator 16. However, it is to be understoodthat the shell 14 can be made of machined cast metal in which case thering 36 can be made integral therewith, thus making unnecessary theindentation 38.

Pressed against the top of the shoulder 34 is an annular shaped spacermember 49 mounted concentrically with the shell 14. A pair of metalgaskets seal between the lower oortion of the shoulder 34 and thesupport ring 36 and between the upper portion of the shoulder 34 and thespacer member The shell 1 the ring as, the spacer 4t and also thegaskets and are all made of some heat-resistant metal such, for example.as stainless steel.

The upper insulator 18 is somewhat similar in construc tion to the lowerinsulator in that it is provided with a center bore 46 having ameter andan extrenal annular shoulder 59. The upper portion 48 of sage isprovided therebetween. The function of this opening will be hereinafterdiscussed. The lower edge of the shoulder 50 rests against the upperedge of the spacer member 40 and the insulator is secured in position bymeans of the shield 22, the lower edge 56 of which abuts and holdspressed against the shoulder 56 a gasket 58 made of copper or some othersuitable metal. A gasket oil, of some heat-resistant metal such asnickel, forms a seal between the spacer 40 and the shoulder 50.

Mounted in the centerbores of the two vertically arranged insulators 16and 18 is the tubular electrode 20 having a hollow center 62 and a pairof cooling air entrance slots 64. The electrode is made of aheat-resistant metal or metal alloy such, for example, as Chromel orInconel.

The lower end 66 of the electrode 20 of unit 8 is bent at an angle ofabout inwardly (to the left as shown) toward the electrode of unit 10,and the lower end 68 of the electrode of unit 10 is also bent at anangle of about 90 inwardly (to the right as shown) toward the electrodeof unit 8. Thus, to this extent the two units difler.

As can best be seen in Figure 1A, the top of the electrode 20 isprovided with a cap 7% having a shank 72 which extends into the hollowcenter of the electrode 24 and is secured thereto by brazing and bypressing a circumferential portion of the electrode inwardly to engage agroove '74 provided in the shank. A slotted head portion '76 of the cap70 cooperates with a shoulder 78 in the bore of the upper insulator tomaintain the electrode vertically positioned. It is preferable toprovide a sealing composition, such as silicate cement 80, between theelectrode and cap assembly and the bore of the insulator. For thepurpose of supplying this cement, a diagonally upwardly (as shown)extending hole 82 is provided in the electrode and cap assembly. Afterthe electrode and cap assembly is positioned in the upper insulator, thesealing composition, such as a silicate cement, is forced through thehollow center 62 of the electrode 26 through the hole 82 and into thespace between the electrode-cap assembly and the wall of the centerbore46 of the upper insulator. When the cement oozes out from the bottom ofthe upper insulator there is assurance that the entire space has beenfilled. The hole 82 is cut upwardly and diagonally at an angle of about45 in order to insure that the cement will be forced upwardly betweenthe cap 70 and the insulator centerbore shoulder 7 8. The cement 80provides a mechanical support of the electrode and also serves to sealthe structure.

A conductive glass seal 84 which has a screw-shaped partially boredelectrical contact 86 embedded therein forms a bond with the walls ofthe insulator bore and with the top of the cap 70 to form a gas-tightseal and an electrical path. Electrical contact with the ignitioncurrent is made through the contact 86. The seal 84 may be of anysuitable composition such, for example, as a mixture of glass and copperor nickel powder.

In order to maintain the electrode concentrically positioned in thelower insulator bore, radially extending circumterentially spaced lugs88 of sufiicient size to contact the insulator inner wall are providedon at least one axial portion of the electrode. It will be noted thatthis structure serves to maintain the centerwire concentric but at thesame time allows a free passage for cooling air beween the electrode andthe insulator. Other means could of course be used in place of the lugs88 to assure that the electrode remains centered in the lower insulatorbore while at the same time permitting the free passage of cooling air.

The spark plug shell is provided with a pair of vertically arrangedopenings 9% and 92. The lower opening 92 allows cooling air to reach thebottom 32 of the lower insulator and also the lower portion of the shell14 thus cooling the lower portions of the shell and lower insulator. Theupper opening 9d, which is aligned with a similar opening 94 in thespacer member 40, provides cooling air for the upper as well as thelower insulator and for the electrode. The air flows through theopenings 9i) and 94 over the top of the lower insulator 16 and againstthe upper insulator 18, through the passage 54 and the slots or openings64 and into the center 62 of the hollow electrode 29 where it is led tospark gap 96. Also, some of the air entering the opening M) will flowbetween the lower insulator and the electrode past the lugs 88. Thus,the air entering the opening 90 effects the cooling of the entire lengthof the electrode as well as the firing tip thereof. As can be seen fromthe drawing, the air flowing through the electrode of unit 8 will bedirected against the end of the electrode of unit and vice versa.

The mounting pad 12, which is welded or brazed to the metal shells ofthe units 3 and 10, is provided with a plurality of holes 93 for thereception of screws or rivets to secure the igniter to a wall of theburner. A suitable air duct, not shown, is provided in the burner tolead the air ii to the openings and 92 in the shells of the units 8 and10.

The igniter is used with a grounded center tap double secondary ignitionsystem, one coil supplying unit 8 and the other, of opposite polarity,supplying unit 10. in this manner, voltages in the order of 40,009 voltsand higher can be used, no part of the circuit being required to carrymore than one-half of the total voltage. Spark gaps of /2 and larger maybe used without the use of a circuit and igniter made bulky, expensiveand inelficient by way of large amounts of insulation.

Figure 5 shows a modification consisting of a single unit having astraight electrode. Except that the electrode is straight as shown at 1%rather than bent, and that the mounting pad 1&2 supports a single unitrather than a pair, the igniter unit is identical to the units 3 and iiishown in Figure 1. Thus, except for these dilferences, the numerals usedfor identification of the structure of Figure 5 are the same as thoseused in conjunction with units 8 and 10 of Figure 1, and the descriptionof these units previously given is applicable to Figure 5.

For use of the embodiments shown by Figure 5, two of the units shown areindividually mounted on a wall of the afterburner in such a way that theends of the respective electrodes form a spark gap of the desired size.Generally it is preferable to mount the individual units ondiametrically opposing Walls of the burner so that the air emitted bythe end of each electrode will be eiiective in cooling the end of theelectrode of the other unit. Of course, if the units are mounted on theburner walls so as to be at an angle to each other, the ends of theelectrodes can be bent the desired amount to direct cooling air into thespark gap.

Separate air ducts are employed to lead cooling air to each of the unitsand just as in the case of the previously described embodiment, agrounded center-tap ignition system is used with each pair of units.

By means of the igniters of this invention, a long spark, that is, aspark on the order of /2 or more can be obtained by the use of highvoltages but without the use of large amounts of electrical insulation.At the same time, adequate cooling means for the entire assembly isprovided by the use of the novel double insulator structure the airpassage structure described.

it is to be understood that, although the invention has been describedwith specific reference to particular embodiments thereof, it is not tobe so limited since changes and alterations therein may be made whichare within the full intended scope of the invention as defined by theappended claims.

I claim:

1. An igniter unit comprising a hollow electrode, an upper insulator anda lower insulator surrounding said electrode, a metal shell surroundingand supporting said insulators and means for cooling said unit, saidmeans comprising an opening through said shell adjacent said lowerinsulator to allow cooling air to circulate past said lower insulatorand a second opening through said shell adjacent said upper insulator toallow cooling air to circulate past said upper insulator and throughsaid hollow electrode.

2. An igniter comprising a pair of units, each of said units including ametal shell, upper and lower centerbored insulators in said shell, saidupper insulator extending into the centerbore of said lower insulatorand leaving passage between said upper and said lower insulators for thecirculation of air, a hollow electrode mounted in the centerbores ofsaid insulators, said electrode having an opening adjacent said passageto allow cooling air to circulate through said electrode, an openingthrough said shell adjacent said passage to allow air to circulate pastsaid upper insulator and into said passage, and a lower opening throughsaid shell to allow air to circulate past said lower insulator, saidunits being mounted together in parallel spaced relationship, the end ofthe electrode of each of said units being bent at and toward the end ofthe electrode of the other of said. units to provide a spark gap and todirect air against the electrode of the other of said units.

3. In an igniter unit, an elongated electrode, an upper insulator and alower insulator surrounding said electrode, each of said insulatorsbeing provided with an annular shoulder, a sheet metal shell surroundingsaid insulators, and means for supporting said insulators in said shell,said means comprising an interior shoulder indented in the wall of saidshell cooperative with said lower insulator shoulder for supporting saidlower insulator and a spacer ring concentrically positioned in saidshell between said lower insulator shoulder and said upper insulatorshoulder for supporting said upper insulator.

4. An igniter comprising a metal shell having upper and lower openingstherethrough, upper and lower insulators with vertically alignedcenterbores mounted in said shell, an electrode in said upper insulatorcenterbore and extending through said lower insulator centerbore, anannular passage between said upper and said lower in sulators andcommunicating with a passage between said electrode and said lowerinsulator, a plurality of radially extending lugs on said electrode tomaintain said elec trode concentric with said lower insulatorcenterbore, said upper opening through said metal shell being adjacentsaid annular passage to allow cooling air to pass between said electrodeand said lower insulator and said lower opening through said metal shellallowing cooling air to pass between said lower insulator and saidshell, and means for sealing and securing the upper end of said electrode in said upper insulator centerbore said means comprising aconductive glass seal bonded to the walls of said upper insulatorcenterbore and in electrical contact with said electrode and a silicatecement between said electrode and the walls of said upper insulatorcenterbore.

5. An igniter comprising a metal shell having upper and lower openingstherethrough, upper and lower insulators having vertically alignedcenterbores mounted in said shell, said upper insulator extending intothe centerbore of said lower insulator, an annular passage between saidupper insulator and said lower insulator adjacent the upper openingthrough said shell, a tubular electrode sealed into the centerbore ofsaid upper insulator and extending concentrically through the centerboreof said lower insulator, said electrode having an air passage throughthe wall thereof adjacent said first mentioned passage, said upperopening allowing air to circulate past said upper insulator and throughsaid electrode and said lower opening allowing air to circulate pastsaid lower insulator to cool said unit.

6. An igniter comprising a pair of units, each of said units including ametal shell, upper and lower ccnterbored insulators in said shell, saidupper insulator extending into the centerbore of said lower insulatorand leaving a passage between said upper and said lower insulators forthe circulation of air, a hollow electrode mounted in the centerbores ofsaid insulators, said electrode having an opening adjacent said passageto allow cooling air to circulate through said electrode, an upperopening through said shell adjacent said passage to allow air tocirculate past said upper insulator and into said passage, and a loweropening through said shell to allow air to circulate past said lowerinsulator, said units being separately mounted in spaced relationship toprovide a spark gap between the electrode of one of said units and theelectrode of the other of said units.

References Cited in the file of this patent UNITED STATES PATENTS

